1. Field of the Invention
The present invention is directed to an implantable medical device having surfaces that are in communication with the tissue of a patient after an implantation, with at least a part of these surfaces provided with at least one layer composed of a medication.
2. Description of the Prior Art
A heart pacemaker electrode is disclosed in U.S. Pat. No. 4,711,251 having a medication layer on its electrode head that has an inflammation-inhibiting effect when the electrode head presses against the heart wall. The growth of fibrous tissue in the region of the electrode head can be avoided or reduced in this way. The disadvantage of the medication layer is that it comes into contact with body fluids during the implantation procedure and is thus at least partially dissolved before the electrode head reaches its ultimate position at the heart wall.
U.S. Pat. No. 4,304,591 discloses a hydrophilic polymer layer that is employed in implantations and serves as carrier for, among other things, medications. In this known arrangement as well, the medication can undesirably separate from the polymer layer when it comes into contact with body fluid.
A heart pacemaker electrode is disclosed in European Application No. 0 388 480 having an electrode head provided with a layer composed of a hydrophilic polymer in which an inflammation-inhibiting steroid is embedded. Although the embedded medication is in fact prevented from prematurely dissolving in this way, the release of this steroid is difficult to control. Moreover, the quantity of medication that can be embedded in the layer is generally too small. When relatively large quantities of a medication are required, the polymer layer must be made so thick that the electrode head can no longer be kept small.